Once the assembly has been fixed together, eg. by gluing, by welding or by compression, it is essential for the three distribution networks (for fuel, for oxidant, and for electrolyte) to be sealed against any leakage between each other and also with the exterior (except in the case of air being used as oxidant, in which case the oxidant distribution network (only) may communicate freely with the exterior).
Unfortunately, the juxtaposed faces of the frames may depart sufficiently from being perfectly plane and parallel to cause sealing problems.
Preferred embodiments of the present invention overcome this problem and provide the desired degree of sealing for the various fluid distribution networks.